Ramco 5.5m Motor Query...

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Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2020 at 6:19am
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Sounds a little light but within the realm of possibility for a 5.5m tinny. I teach maths and physics and can vouch for Steps method: standard torque calc. Wouldn’t use it myself because accurately measuring is tricky and the local weighbridge is free to use.
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2020 at 8:07am
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Titanium
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612kg yes seems a bit light

Put the motor down....
The trailer is level?
 Ground level?

take 612kg start adding bodies say 32X 85kg =170kg
 Throw in fish bin bait burley ice etc all mounts up. it is getting up to your estimate.

 Weigh bridge.. well you need to know its been  re calibrated regularly..
 And dropping the boat off the trailer then re load, not difficult but still a issue.
 Then there is as I calculated before based on Newtons  2nd law (think it is) , about a object of a given weight will move at a constant speed at a given force.

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Post Options Post Options   Likes (0) Likes(0)   Quote OuttaHere Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2020 at 12:57pm
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It sound about right to me. There is not a lot to these boats. Relatively thin alloy, horizontal supports only under the floor, and a simple structure. Tow weight for a Fyran Horizon 560 (slightly larger, more complicated boat) is 955kg; subtract roughly 300kg of trailer and you're there or thereabouts.

612kg boat + 200kg of crew and loadout.... 850kg with some room for gremlins...

I feel like we need to gather and contribute some more accurate data to Steps' database for boats in this bracket; I don't know if its the hull design or what but the numbers don't quite tally.
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Post Options Post Options   Likes (0) Likes(0)   Quote Maydogg Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2020 at 1:28pm
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Yep - I agree on gathering more info for boats. The more info for future use and decision making the better for all.

Roz - you are correct in that these dominators are pretty simple and are slender, with not a lot of over engineering at all.

For a true weight I may take out the fuel and extra bits and pieces. Just leave anchor, rope and batteries in.

Will take the measurements again this eve and put the motor down as far as I can.

I'll find out my trailer weight also - would be interesting.

Jason
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2020 at 4:33pm
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I feel like we need to gather and contribute some more accurate data to Steps' database for boats in this bracket;

Have been building it up over the yrs From data provided privately and guys who put up good data in the forums when asked.
There are not many  NZ hulls between about the 4.8 to 6.5m planing hulls I have not got.
 In this case its (I think) the older hull model ??
Its establishing the hull constant at cruise and WoT. There is little difference in  most trailer boats due to limitations on towing/ beam. But a factor of 5 can made that little didference.
If we where powering and propping to get that fine 0.2 of a sec on a race coarse to get a checked flag, then the constant hast to be far more accurate than  a general use type boat we deal with in these forums.

For a true weight I may take out the fuel and extra bits and pieces. Just leave anchor, rope and batteries in.

 Load and stow the boat up, fuel gear  etc as close to what it would be on the water.. even the usual ppl in their normal position when cruising would be the ideal.


Will add here  it can be done on a duel axle trailer.. just remove , or have 1 set wheels up off the ground

Also maybe of interest... when I compare the tow weight specs, including the engine weight of most boats in the 5 to 6.5m range, by coincidence, it comes out to damn near the general gross weight on the water Wink give or take a person.
 
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Post Options Post Options   Likes (0) Likes(0)   Quote ofthesea Quote  Post ReplyReply Direct Link To This Post Posted: 12 Sep 2020 at 9:21am
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Permatrim definitely helps some boats
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 12 Sep 2020 at 9:47am
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With all due respect NO..
If you have a under powered boat.. or put another way  a hull that has a engine not suitable for purpose.. like doing long haulage with a mini tractor unit.. then yeah.

If they where good  manufactures would be selling them under their brand name
 They would also cover warrentees when used
They would provide holes to fit.
 They would mention fitting use in manuals  etc. 
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Post Options Post Options   Likes (0) Likes(0)   Quote Maydogg Quote  Post ReplyReply Direct Link To This Post Posted: 12 Sep 2020 at 5:15pm
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Hey guys,

Cheers for all the chat - it’s been good banter and some interesting things to think about.

Steps - I believe my hull is a 1995 from memory?

I did the measurements and weights again. Unfortunately as my trim system is a bit stuffed there was only so far I could put it down and the manual screw under the motor to release the trim is a bit seized. It’s plastic and don’t want to strip it.





W1 207.4lb
D1 15.157”
W2 72.8lb
D2 173.228”

= 1538.33lb or 697.77kg

Seems a little better potentially?
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 2020 at 9:58am
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yep sounds pretty close to spot on. Throw in 3 guys , bit gear and 950 ball park.
 If things seized up, do you have full trim from right down when take off and adjust up as speed increases?

Get in with some non petroleum based  inox, spray, repeat once a day for a week.. then gently see what frees up.

 Once freed up. under cowl maintain a fine , mist spray of lanocoate .. absolute minin , as little as possible foe the thinnest cover.. Yeah sound over board explanation, but the other day, someone followed my 'instructions' without taking notice of  "mist" and did good coverage and now have a hard covering..
 Same around the trim area...
and wiring back of the dash panel little heavier but no need to maintance re apply

Just had a thought thu.. bathroom scales.. I watch my weight every morning before a shower...A couple/ few yrs back needed new scales and suddenly I put on 1.5kg.
 
 Had a dr. appointment so weighed myself, then again at the docs.. 1.5kg heavier on the new scales.
Went to the shop and they just hedged the issue.
 So off to another branch, pulled out every brand and put on the floor in a line. Compared weights (I knew my real weight)  sure enough , 1/3 of the brands read between 1.3 and 1.5 heavier than actual. 

If checking yours check at around 75/85kg weight..1L water=1kg.
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Post Options Post Options   Likes (0) Likes(0)   Quote Maydogg Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 2020 at 4:17pm
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Hi Steps

Originally posted by Steps Steps wrote:


 If things seized up, do you have full trim from right down when take off and adjust up as speed increases?

I just released it with marine CRC and an Impact Driver hand screwdriver set. Managed to get the motor a few inches off the ground and it stayed there through the testing process.

In terms of running motor when on water - I dont always have the motor right down, even trimmed up a bit it usually has enough torque to get out of hole. I believe the 60 Bigfoot has the larger 115hp bottom end?

Interesting to note - the motor sprays a lot of water out the sides until you have it almost trimmed all the way up as if something is catching in the water.

Originally posted by Steps Steps wrote:

If checking yours check at around 75/85kg weight..1L water=1kg.

I checked with what I could find around the house - I don't know my exact weight, so just used a few different smaller weights to get an idea.

5l house wash concentrate unopened = 5.5kg but also a little bit of weight for the plastic bottle etc.

I measure a 10 kg and 14 kg kettle bell both came out at 9.9 kg and 13.9 kg respectively.

Having the engine down just off the ground this time with seats back in the boat, all usual gear 80l chilli bin (not full) and 30 odd litres of fuel.

You will notice all the hydraulic fluid leaking.





W1 207.8lbs
D1 15.95"
W2 68.6lbs
D2 174.01"

= 1518.63lb = 689 kg (rounded)

Based on this - is a 60hp suitable?


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Post Options Post Options   Likes (1) Likes(1)   Quote OuttaHere Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 2020 at 9:12am
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Maybe a dumb question.... but honestly everything except the trim motor/pump looks reasonably good in there, have you thought about just replacing that part? If you've been quoted more than $1000 to do that (and even that feels expensive) you're being fleeced.
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 2020 at 9:20am
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In terms of running motor when on water - I dont always have the motor right down, even trimmed up a bit it usually has enough torque to get out of hole. I believe the 60 Bigfoot has the larger 115hp bottom end?

Trim:
 Trim is what you use far more often than the throttle.
At still, the trim is right down, if it is not the boat struggles to get over the bow wave.. basically crap hole shot if up, even a little up.
 Also it trim is up and moving off the plane down thru boats or a creek, your steering is crap
The boat goes over the bow wave and onto the plane, now you bring the trim up to just before ventation.. should be able to hear it, and/ or porpoising (bow bouncing excessively)
If this is not the cruise speed you want then increase rpms to just below for that cruise speed.. then trim up. the rpms and speed increase due to more push and less drag.
Well trimmed saves a huge amount of fuel.
 If slow a little by throttle, drop the trim accordingly.

You are at a cruise speed, a wave comes up you have to cross.. line up and just before, drop the trim. Bow drops, speed drops and you go over smooth.. All with trim button... withing commonsense reason of course.

Get into chop, may have to drop throttle a little, if small chop simply dropping trim slightly keeps a reasonable comfortable ride at good planing speed and economy without falling off the plane.

Faster you go, the more you can trim for that faster speed

Manufactures design their trims, engine size to be fitted so hulls are well powered.. by weight.

Displacement hulls are a totally different kettle of fish.

Yeah looks like total gross weight, by estimate ,and by an estimated calc of WoT  due to possible not trimmed was well as should and revised hull constant would come in at about 950kg.

60hp 2S will give a WoT around 32 mph 4S  34 mph
75 2S  about 36 mph  4S  38 mph
90 2S  about 40 mph 90   4S  42 mph

A nicely powered you would have a WoT around 38mph
Well powered 42 mph

To get the best out of your hull on that boat with that loading a min 90 2S or 4S
 This is all based on performance economy, weight etc
 Not manufactures construction specs which I do not know.

The difference even between a manufactures mid of the hp range (usually min powered by weight) and their max hp rating in hull performance is HUGE in most cases. Thu some manufactures have trouble meeting Safety specs and even their max powered rating is still mediocre

 I hope this info gives you the information as to  fix trim or repower, and if re power what to repower to.

I strongly advise, even if bit over budget, and intend to keep the boat for a long time... repower well.

If re power low, and going to sell.. do what some (far too many) sale yards do.. strip as much weight out, use a light weight sales rep to demo/ sea trial and dump a prop on next pitch up. Wink

One of my most disheartening things are ppl who contact me..And this includes experienced guys surprisingly too often
 " my new boat doesnt go as well as when we trialed or in reveiws... Can we change props to make it do so"
 They are on budget, gone for as much boat and compromised on power in the total price...
This is their pride joy.. gone for broke..
 And I have to explain something they just dont wish to acknowledge or have issues excepting...
Im not a diplomatic person, and it hurts my heart when I do so.

As to building my data base..
alloy boats from the 90s period in particular when manufactures went from thin light panels to thicker welded panels, more weight, and hulls dont get 1000s of pin holes, is a bit confusing due to significant changes in weights.
 These days alloy and glass hulls are very similar in weight, differences are in things like cabin or not in both cases.


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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 2020 at 10:21am
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Titanium
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Originally posted by Rozboon Rozboon wrote:

Maybe a dumb question.... but honestly everything except the trim motor/pump looks reasonably good in there, have you thought about just replacing that part? If you've been quoted more than $1000 to do that (and even that feels expensive) you're being fleeced.


Also along my thoughts..A set new seals, clean up...its a job I would be looking at doing myself, even thu never done a outboard hydrolic trim before..Even just the R&R .. shop around
 And do a serch in these forums on the subject.. Im sure from memory there are old threads from over the yrs.. with pics  what where how
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Post Options Post Options   Likes (0) Likes(0)   Quote johnybegood Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 2020 at 4:00pm
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For what it's worth I have a trim unit that looks the same as yours sitting in the shed. I purchased it as the ram on mine leaked so I took the parts I needed and did it myself. Flick me a message if the trim unit is of interest - it's from a 2004 mercury 115 4 stroke, no rust
I just want to jig
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Post Options Post Options   Likes (1) Likes(1)   Quote jackel Quote  Post ReplyReply Direct Link To This Post Posted: 17 Sep 2020 at 6:33pm
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Hey I'm going to suggest a really simple solution. I have a 5.6 Ramco Interceptor with a 90Hp 2 stroke which I think goes well for me anyway. Certainly not under powered for what use it for. (I dont think it exceeds manufacturer weight, but would be interested to know if it is). I prefer a seat of the pants type testing, track down someone with the same hull and different outboards, jump on board with them and see how it goes with a similar load. I'm not one for doing 25 complicated calculations to come out with a result that may be incorrect, if any one of the baseline data are wrong. 
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